Preparation of 2, 2-bis (p-chlorophenyl) 1, 1, 1-trichloroethane



atented cc, 7,,

PREPARATION or 2,2-BIS (r-cnnoao- PHENYL) 'LLI-TRICRLOROETHANE Adrian C. Smith, Philadelphia, and Julian L.

Staubly,

Drexel Hill,

Pa, assignors to The Pennsylvania Salt Manufacturing Company,

Philadelphia, Pa" vania a corporation of Pennsyl- No Drawing. Application July 1%, 19%, Serial No. states 8 ms. (El. 260-649) E The present invention relates to the synthesis of 2,2, bis (p-chlorophenyl) 1,1,1, trichloroethane (DDT) and more particularly it relates to the preparation of this compound from trichloro- An object of this invention is to provide a process for the preparation of DDT from chloral and monochlorobenzene in a simple and economical manner with high yields of a, product of high acetaldehyde (chloral) and monochlorobenzene 5 puglliytg d glip gv flie -1 t1 1 t m employing a condensing agent under specified 0 er 0 cc 0 s nven on s o prov e conditions to effect th reaction, a condensing agent which will effect the conden- DDT, first prepared many years ago, Zeidler, satlon of chloral and monochlorobenzene in a Ber. 7, 1180-1, 1374, has, within the past few simple and efiicient manner to form DDT avoidyears, become an increasingly important insectiing, to a great extent, side-reactions and elimicide. It is also employed for other purposes and n tin entirely the formation f sulfoneled ythere is, at present, need for a more emcient productsmethod of peparfationbinsurgig thigher yiells of A 2 1 gl t i l'l g nt shto D g/lie the product ree rom y-pro uc s and con ense 001! 6 ng S W C W 8 e0 8 Con e ing agent residues. sation of chloral and monochlorobenzene to form In the prior art method of preparation chloro- DDT n Which can be readily a d ti lly benzene and chloral were condensed employing fl p y recovered f reuse. sulfuric acid as the condensing agent. Four or other o j and advantages a e ppa ent five volumes of concentrated sulfuric acid were m this specification d the Claimsmixed along time with active agitation occa- According t the v t on. chloral and monosionally warming in a water bath. When a white, chlorobenzene e condensed n eact n p oporputty-like mass no longer;i sepalrated, the whole 233: (1 252 2 32 o l lliiglig g g ezfi y reaction mass was washe wt water and re- 8 c crystallized from hot ether-alcohol. t hydrofluoric c d as t c nde sin agent 1 s patent 2 329 07 discloses the followin it is possible to obtain high yields of products of preparation: By treating, while strongly stirring, high purity and improved odor- The acid can be a mixture of 2 molecules of benzene or chlororeadily and Substantially completely recovered benzene with 1 molecule of chloral or chlorals? importantladvantages over the hydrate with an excess of concentrated sulfuric 3; c employs r3110 acid g 5 g acid (of 100% strength) heating takes place after so i fi gg fig g 2 3; gg 25; 32 21 2 3 gg ig ggigggizfii gf gg gz gl Also, the purification process is much simplified. ti This is important when the insecticide and other nued until the reaction mass has cooled down to uses to which DDT is put are considered For room temperature and contains 50nd pantcles' example,aproduct containing acid impurity; used Then it is poured into much water whereby the on foliage, will destroy the leaf. It is therefore, raw condensation product separates out in a solid necessary m such case to empluy expensive equip form. It is well washed out and, after being ment to purify the product The product of the recrystallized from alcohol, it is obtained in form present invention is as stated substantially free of a fine crystals which Show a weakly fruit 40 from appreciable quantities of acid and consequently. does not require the expensive purifica- The crude product obtained by the prim" art tion that is necessary in the case of DDT prepared method described contains, besides other impuriemploying ulfuri acid a th condensing agent. ties, sulfuric acid which is difllcult to remove. The broad cohcept of this invention is that Also, the sulfuric acid attacks the benzene ring, hydrofluo i acid is employed as the condensing Yiel in O j i n Sulfoneted r v s agent. Anhydrous hydrogen fluoride is preferred wh1 h, f Course. a t he yield of DDT. There but strong concentrations of hydrofluoric acid is a concomitant loss of sulfuric acid and monoare operative, the yield of DDT increasing with chlorobenzene and these losses add to the cost of increased concentrations of HF in the acid althe preparation. though DDT has been obtained employing 94% aeeaeee HF acid. In the claims, the expression hydrogen fluoride containing not more than about 6% water" is used to include both this highly con- Iflect of ratio of .chlorobenzene to chloral benzene although it is equally apparent that the process will yield good results when stoichiometric quantities of the reactants are employed.

Team: 11

[Temperature 80' (3.; ratio HF/CCI..CHO 68 :1 duration 18 hours] centrated hydrofluoric acid and anhydrous hydroaen fluoride. The quantity hydrogen fluoride employed should be at least sufficient to insure a Moi Per n Cent Moi Per Cent Moi Per Cent w m 'age Set Me s M L states" 1 o ore cm a Resid (pure) DT) DDT chloral reacted) m 4a: at eao 1.90 ess :1 I 1M .6- 141 70-6 Agitation plays an important part in the con- 20 densation reaction. As will appear hereinaiter,

mol ratio HF/CChCI-IO 0! about 90 although a mol ratio as low as is operative. Preferably, as is indicated by Table I. the mol ratio of E! to the condensing agent and the reactants are not miscible and to insure intimate contact agitation is necessary. The eflect of agitation upon the reaction is indicated in Table III.

Team 111 Eflect of agitation [Temperature -29'C.: ratio HF/ CCI..CHO 68 :1: duration 18 hours] 4 sum a a net-maul angle oi degrees to the direction 0! stroke. See below.

CCleCHO will be at least about and can be more, say or even higher.

TAIL! I Time also plays an important part in the re- 45 action. At room temperature 45.2 mol percent 01 Ifleet 0] the mol ratio HF/CClsCHO [Temperature 80 0.; reactant ratio Camel/0011.030 2: I accept last experiment] Moi Per Cent Mo] Per Cent HF Per cent Conversion oi ure DDT Yi ld of we Ratio Cent DDT Residue Calcum, to crude Bath p R 1 DDT Based on oclrono (pm) T) DD as due chlorai reacted) 11.2 11.0 so. 4 87.4 '0. s34 45. 4 23.4- 83.4 38.5 61.9 1.18 64.1 45. 3 40.3 29. 1 75. 4 1. 59 61. B 68.0 46.3 33.8 .0 1.90 65.5 i 90. 6 59. 0 (23. 6) (81. 6) (2. 61) (72. 3)

1 Temperature 47-60.

Reactent ratio 2%: l. Estimated values.

DDT was formed after 18 hours and after 64 hours 69.1 mol-percent was obtained. At a higher temperature, in 1% and in 2% hours, 57.2 mol percent and 64.5 mol percent DDT respectively were formed. Time and temperature are, therefore,

- dependent variables. The higher the temperature, the more rapid will be the overall reaction rate and vice versa. The eiiect oi. time is shown by Table IV and the effect 0! temperature is shown in Table V.

TABLE IV Efi'ect of time [Temperature 80 C. and 75' (2.: reactant ratio 2: 1 and 2% :1; ratio HF/CCbCHO 68: 1]

Mo] Per M] Per Cent Moi Per Cent Mol Per Cent s a um c ore cru Res due ass on (pure) land as DDT) DDT chlor reacted) 18 45. 2 23. 8 B9. 0 1. Q0 66. 6 64 d9. 1 24. 9 84. 0 2. 87 70. 4 1 57. 2 26. 1 82. 8 2. 21 69. 6 2 64. 5 26. 6 so. 1 2. 42 71. 5 3 64. 6 28. 8 93. 8 2. 24 68. 6

TABLE V E Tect of temperature HF per mol. oi CCL.CHO; agita- [Tlie system: Chloral-chlorohenzene-HF 88 mole of tion endover end] Mol Per Mol Per Cent M01 Per Cent Temp, Cent g Conversion of R n pure DDT Duration, Yield of pure C. DDT a a 5%. chloral to crude a o R i Hours DD'I Based on (pure) 8 as DDT chlora reacted) '8 56. 3 34. 0 90. 3 L 65 1% 62. 5 75 64-6 26-6 90. 1 2.42 2 71. 6 17-50 53. 2 22. 6 75. 8 2. 4 70. 3 80 45. 2 23. 8 69. 0 1. 90 18 65. 5 m 52. 6 21- 5 74. O 2. 44 24 l 71. 0

i Agitation on shaking machine. (See below.)

While an increase in temperature will cause an increase in the overall reaction rate from 7.0% in 24. hours, at 23-8 C. to 90.3% in 1% hours at 96-8 (3., it appears that at the higher temperatures the yield of DDT is actually lower. At room temperature the reaction rate seems to be impractically slow. A practical operating temperature now seems to be within the range of a0" (Ii-85 C.

In the following description of general experimental procedure it will be noted that the condensation is efi'ected at the pressure of the reactants corresponding to the temperature employed. Thus, the condensation is eiiected substantially in the liquid phase. This should not be interpreted to mean that the invention does not include condensation at subatmospheric or atmospheric or even high pressures, the essence of the invention being that hydrogen fluoride or hydrofluoric acid is employed as a condensing agent for the reaction to produce DDT from chloral and monochlorobenzene.

The following experimental procedure which has been employed is set forth by way of illustration and the invention is not to be limited thereto.

Heavy copper pressure bottles were first charged with a quarter mol of chloral and 0.5 to 1.0 mol oi chlorobenzene. The bottle was packed in ice and salt and the whole was balanced on a suitable scale. Gaseous HF was then introduced into the cold bottle where it liquefied and the rate of addition was followed by the gain in weight. When the required quantity of EB had been weighed in, a plug was quickly screwed into the bottle;

The charged pressure bottle was then fixed to a shaking machine or to a wheel rolling in a thermostatically controlled (:2) water bath and there maintained during the designated time intervals at the end of which the bottle was again packed in ice thereby effectually inhibiting further reaction and making it possible to open the cylinder with relative safety. (The shaking machine used in this study had a three inch stroke and made 180 or 280 complete courses per minute. The

wheel used in the water bath had a 42 inch diameter and turned the bottles just inside its circumference end over end 14 times per minute.)

The bottle contents were poured into cracked ice, and if the organic layer drained completely from the reactor (indicating very incomplete reaction) it was washed several times by decantetion and steamed. If practically nothing except liquid HF drained from the bottle, a good reaction had occurred as indicated by a solid mass remaining inside, and this mass was removed by solvent action. A good solvent for the purpose is methyl ethyl ketone.

The cake of organic material separated from the solvent (e. g. by mixing with water in the case of the ketone solvent) and neutralizing (e. g. by washing with a sodium carbonate solution) was rinsed with a little fresh water, transferred to a steam distillation flask and steamed. The steamed organic residue was poured into a beaker and again allowed to harden. The mass was porous and contained 5 or 10% of mechanically held moisture and at this stage it was best to break up the cake and to dry for about an hour at 50 C. Then it was weighed, transferred to a flask, and isopropanol was added. The flask was DDT were crushed to facilitate solution and after complete solution, crystallization, directly in the flask or following filtration through a loose plug of cotton, occurred on cooling. (A' fixed' lower temperature of 5 was attained before separating the crystallized DDT.) The mass of needles was broken up again and placed on a filter, care being taken to obtain quantitative transfer. The cake of crystalline DDT was suitably compressed and when the drainage of the isopropanol liquor practically ceased at the diminished pressure of the water pump, the solid was spread out and dried at 50 C. to absence of alcohol odor or constant weight. DDT obtained in this way usually melted not lower than 103 C. I

The isopropanol filtrate was gently evaporated to constant weight and the weight of non-crystal-= lizing residual oil was a good measure 01' side reactions which occurred during the synthesis.

Inthe foregoing tables yields and ratios have been calculated on a mol basis since conversion to other units is then readily possible. For example, 74 mols of HF to 1 mol of chloral is a weight ratio or 10 to 1 since X74/147.5=10. Similarly 2.2 mols or chlorobenzene to 1 moi of chloral is a weight ratio or 1.68 to 1 since 2.2x 112.5/ 147.5= 1.68. The oil residues remaining after the removal of crystalline DDT have been calculated arbitrarily on a moi basis as though the residue were DDT. The sum of the DDT plus the residue is assumed to be the extent of total reaction. The yield of DDT actually isolated, divided by total reaction, gives a figure for total .possible DDT obtainable if reaction had gone 100% and is included in. Tables I to V. Unreacted chlorobenzene, separated by steaming the primary reaction batch, is also an index of total reaction but is only approximate due to mechanical and vapor losses.

The ratio of crystallized DDT to oil residue is included since it significantly shows the relative purity of DDT obtainable under varying conditions.

In the following claims DDT'? is to be interpreted to include 2,2 bis (p-chlorophenyl) 1,1,1,

trichloroethane. Also, where, in the .claims, hy-.

drogen fluoride occurs, it is to be understood that hydrofluoric acid is included.

The invention can be practised employing chloral hydrate or even chloral alcoholate in place or chloral and in the claims chloral hydrate and chloral alcoholate are included in the term chloral."

Modifications within the skill of those versed in the art are obviously within the appended claims and are therefore not discussed here.

We claim:

1. A method of producing DDT which com- .prises condensing chloral with chlorobenzene in the presence of hydrogen fluoride, the quantity or hydrogen fluoride being at least 10 times as great as the quantity or chloral, on a molar basis.

2. The process according to claim 1 wherein substantially anyhdrous hydrogen fluoride is employed.

3. The process according to claim 1 wherein the temperature during said condensation is maintained within the range of about 40 C. to 85 C.

4. The process according to claim 1 wherein the quantity of HF ranges from about 10 to 100 times as great as the quantity of chloral, on a molar basis.

5. The process according to claim 1 wherein approximately stoichiometric quantities or chloral and monochlorobenzene for reaction to form DDT are employed.

6. The process according to claim 1 wherein an excess oi monochlorobenzene over the stoichiometric quantity for reaction with the chloral to form DDT is employed.

'1. A process for the preparation oi DDT which comprises bringing together chloral, monochlorobenzene and liquid phase hydrogen fluoride containing not more than about 6% water, the quantity of HF being at least 10 times as great as the quantity of chloral, on a molar basis, agitating the mixture under conditions wherein the reactants are maintained essentially in the liquid state, to bring about condensation of the chloral and monochlorobenzene in a liquid phase reaction, and separating the DDT from the resulting reaction product.

8. A process for preparation of DDT which comprises bringing together chloral, monochlorobenzene, and substantially anhydrous liquid phase hydrogeniluoride, approximately stoichiometric quantities of chloral and monochlorobenzene for reaction to form DD'I" being employed and the quantity of HF ranging from about 10 to times as great as the quantity of chloral, on a molar basis, agitating and warming the resultant mixture while maintaining it under conditions wherein. the reactants remain essentially in the liquid state, to bring about condensation of the chloral and monochlorobenzene in a liquid phase reaction, and after condensation has been substantially completed heating the resulting reaction mixture to separate the HF from the DUI product.

ADRIAN C. SMITH. JULIAN L. STAUBLY.

REFERENCES CITED The following references are of record in the flie of this patent:

UNITED STATES PATENTS Number Name Date 1,961,397 Schoeller et a1 June 5, 1934 2,329,074 Muller Sept. 7, 1943 OTHER REFERENCES Bimons, "Industrial and Engineering Chemistry, vol. 32, pages 178-83 (1940). 

